Attacks on the world's seas are soaring as armed and dangerous pirates become increasingly emboldened, seizing more ships than before and taking even bigger risks, an international body said.

Attacks on the world's seas are soaring as armed and dangerous pirates become increasingly emboldened, seizing more ships than before and taking even bigger risks, an international body said.

In the first six months of 2011, there were 266 piracy attacks compared with 196 incidents over the same period last year, and 60 percent of them were carried out by Somali pirates, the International Maritime Bureau (IMB) said.

At the end of June, Somali pirates were still holding 20 vessels and 420 crew, and demanding millions of dollars for their release, the IMB's piracy reporting centre said.

IMB director Pottengal Mukundan warned ship owners and captains to be on their guard as pirates are using new methods and even carrying out attacks in bad weather.